Hole-saw

Abstract

A hole-saw comprises a tubular body connectable at one end to inter alia a power drill and formed at its other end with an annular array of cutting teeth. A collar is positioned at the end of the tubular body remote from the cutting teeth, the perimeter of the collar extending generally normal to and beyond the perimeter of the tubular body.

The invention claimed is: 
     
       1. A hole-saw which comprises an open-ended tubular body releasably connectable at one open end to a power drill and formed at its other open end with an array of cutting teeth, wherein the open-ended tubular body comprises an annular collar positioned at the one open end of the open-ended tubular body remote from the array of cutting teeth whose perimeter extends generally normal to and beyond the perimeter of the open-ended tubular body in a direction normal to the open-ended tubular body, the hole-saw further comprising a drive plate connectable to a power drill and including locating pins upstanding from a surface of the drive plate, recesses formed in said annular collar and positioned to receive said locating pins, wherein when the locating pins are at the recesses is when the drive plate is locked to the hole-saw, and a lining of an intumescent containing material at an interior of said open-ended tubular body, wherein the open-ended tubular body is configured such that on release of the open-ended tubular body from the drive plate following completion of a hole forming operation the hole-saw including the lining of the intumescent containing material remains in a formed hole resulting from the hole forming operation. 
     
     
       2. The hole-saw as claimed in  claim 1  wherein the inner surface of the annular collar includes at least two recesses which coincide with the positions of the locating pins which protrude from the surface of the drive plate. 
     
     
       3. The hole-saw as claimed in  claim 1  wherein the external surface of the open-ended tubular body is at least partially lined with an abrasive material. 
     
     
       4. A hole-saw which comprises an open-ended tubular body releasably connectable at one open end to a power drill and formed at its other open end with an array of cutting teeth, wherein the open-ended tubular body comprises an annular collar positioned at the open end of the open-ended tubular body remote from the array of cutting teeth whose perimeter extends generally normal to and beyond the perimeter of the open-ended tubular body in a direction normal to the open-ended tubular body, the hole-saw further comprising a drive plate connectable to a power drill and including locating pins upstanding from a surface of the drive plate, recesses formed in said annular collar and positioned to receive said locating pins, wherein when the locating pins are at the recesses is when the drive plate is locked to the hole-saw, and a lining of an intumescent containing material at an interior of said open-ended tubular body, wherein the open-ended tubular body is configured such that on release of the open-ended tubular body from the drive plate following completion of a hole forming operation the hole-saw including the lining of the intumescent containing material remains in a formed hole resulting from the hole forming operation, and wherein a piece of sponge material coated with intumescent material is positioned across the end of the tubular body remote from the cutting teeth and is formed with an opening through which a drill of the power tool can pass.